1. Field of the invention
This invention relates to an apparatus for microscopic analysis of phase objects, and, more particularly, to a microscope based on moire deflectometry.
2. Description of the Prior Art
The analysis of phase objects by optical methods has a long and interesting history. A large number of these methods have been developed and are in common use today. These include: interferometry (M. Born and E. Wolf, Principle of Optics (Pergamon, New York, 1970), pp. 256-370); holography; schlieren (F.A. Jenkins and H.E. White, Fundamentals of Optics, Fourth Edition, (McGraw-Hill, New York, 1976)); shadography (M. Born and E. Wolf, op. cit. p. 425; phase contrast (F. Zernike, Z. Tech. Phys. 16, 454 (1935); Physica 9, 686 (1942); and moire deflectometry (0. Kafri "Noncoherent Method for Mapping Phase Objects," Optics Letters 5, 555 (1980), and U.S. Pat. 4,459,027, issued July 10, 1984, to Kafri et al.). Optical analysis of phase objects has special significance in optical microscopy. In fact, phase contrast methods were originally developed for contrast enhancement in microscopy. Early applications permitted the detailed observation of difficult-to-stain biological samples. Today, applications of phase contrast microscopy extend to all fields of materials science, solid state physics, electrical engineering, and to more specialized areas, such as stress analysis and quality control.
Of the methods mentioned above, phase contrast, schlieren and interferometry have particular utility in microscopy. Both phase contrast and schlieren techniques are relatively simple to apply and can be readily adapted to nearly any existing microscope. However, both techniques are only semiquantitive; i.e., they do not give direct absolute measurements of phase distortion. In many applications, qualitative phase information is not always sufficient, but fully quantitative techniques such as interference microscopy can be both cumbersome to apply and expensive.